Problem: 6 folders cost $4.98. Which equation would help determine the cost of 10 folders?
Solution: There are several equations that could help determine the cost, each with a slightly different approach. We know the cost of 6 folders. We want to know the cost of 10 folders. We can write the numbers of folders as a proportion: $\dfrac{6}{10}$ We know 6 folders costs $4.98. We can let $x$ represent the unknown cost of 10 folders. The proportion of these costs can be expressed as: $\dfrac{\$4.98}{x}$ The cost changes along with the number of folders purchased, and so the two proportions are equivalent. $\dfrac{6}{10} = \dfrac{\$4.98}{x}$